What’s the most obscure web based mmo game that you know of that’s still running. (opens in new tab)

It really depends on where exactly you draw the line between graphical MUDs and MMOs. Of those that most sources would agree fall on the "MMO" side of that line, I suspect Nexus: The Kingdom of Winds or one of the other miscellaneous Nexon titles that's inexplicably still up and running would take the prize.